I just realized that the “Show line coverage statistics after test” option doesn’t work for me either. When I pick line coverage it won’t show the coverage statistics and it won’t say that randomtest passed and the time. (It seems like the “Automatically scroll to the bottom” option doesn’t work, too, but that doesn’t stop it from showing that randomtest passed or how long the test took.)
From what I can tell this is because of the recent firefox updates. I use the upload/non-node method like @Brian_Rushton did, so I’m not sure if that has anything to do with it.